Scientists and security specialists are in the midst of a fierce debate over recent experiments on a strain of bird flu virus that made it more contagious.

The big question: Should the results be made public?

Critics say doing so could potentially reveal how to make powerful new bioweapons.

The H5N1 virus has been circulating among birds and other animals in recent years. It's also infected about 500 people. More than half died. But this dangerous virus has not caused widespread human disease because, so far, sick people haven't been very contagious.

If the virus evolves to spread as easily between people as seasonal flu, however, it could cause a devastating global pandemic. So in an attempt to stay ahead of H5N1, scientists have been tweaking its genes in the lab to learn more about how this virus works, and what it is capable of.

In September, one scientist made a stunning announcement. At a flu conference held in Malta, he said he'd done a lab experiment that resulted in bird flu virus becoming highly contagious between ferrets — the animal model used to study human flu infection. It seemed that just five mutations did the trick.

News of the results raised red flags for Dr. Thomas Inglesby, a bioterrorism expert and director of the Center for Biosecurity of the University of Pittsburgh Medical Center.

"It's just a bad idea for scientists to turn a lethal virus into a lethal and highly contagious virus. And it's a second bad idea for them to publish how they did it so others can copy it," says Inglesby.

No science journal has published the information yet. And Inglesby hopes none of them do.

Biology research usually has a culture of openness. Scientists report their methods and results so others can repeat their work and learn from it.

Inglesby agrees that's the way to go the vast majority of the time. But not this time. "There are some cases that I think are worth an exception to that otherwise very important scientific principle," he says. "I can only imagine that the process of deliberating about the publication of these findings is quite serious."

The researcher who presented these findings at the science meeting is virologist Ron Fouchier, of the Erasmus Medical Center in the Netherlands. NPR has learned that his work is now under scrutiny by a committee called the National Science Advisory Board for Biosecurity.

That's a committee of independent experts the U. S. government set up to give advice on how to deal with biological research that's legitimately important to science but that also could be misused. It can make nonbinding recommendations about such things as whether the findings should be published.

NPR asked Fouchier by email if he intended to publish the details of his study. He replied that he preferred not to comment until the committee made a formal decision.

Research on new and worrisome forms of influenza is a case study showing how, a decade after 9/11 and the anthrax attacks, scientists are still grappling with how to handle sensitive biological research, says John Steinbruner, director of the Center for International and Security Studies at the University of Maryland.

"We really do need to develop a better oversight process and a better way of organizing global judgments about very, very dangerous lines of research," says Steinbruner. "And we haven't yet done it."

Scientists say they do think hard about these issues. Princeton's Lynn Enquist, editor in chief of the Journal of Virology, says he and his colleagues carefully considered whether to publish a flu study submitted to the journal that appears in the December issue.

"You have to say, 'Is there more benefit than there is risk?' and that was our judgment on this one, that that was indeed the case," says Enquist.

In that experiment, researchers had taken a bird flu gene and put it in the swine flu virus that started spreading between people a couple of years ago. Mice infected with this lab-created virus got very, very sick.

But Enquist says, this altered virus didn't spread easily. And he points out that this kind of virus combination could happen as bird flu circulates out in nature.

"Scientists in the United States and all around the world are very curious as to how this thing is going to evolve because we have to be prepared for it," says Enquist. "The public would expect us to be prepared."

As part of that effort to get ready, scientists from the Centers for Disease Control and Prevention have been doing work to see how bird flu could adapt to humans. This month, in a different journal called Virology, they described how they created two new versions of the bird flu virus that could spread between ferrets in a limited way.

A spokesperson said no one from the CDC would be made available to comment. And efforts to speak with officials at the National Institutes of Health, which funds flu research, were unsuccessful.